"The present seems to be the most propitious time since the commencement of the war for the Confederate Army to enter Maryland ... we cannot afford to be idle, and though weaker than our opponents in men and military equipments, must endeavor to harass if we cannot destroy them. I am aware that the movement is attended with much risk, yet I do not consider success impossible ..."
- Robert E. Lee, in a letter to President Jefferson Davis, 3 September 1862
After a very successful summer of fighting in the Peninsula and 2nd Bull Run campaigns, General Robert E. Lee and his Army of Northern Virginia (ANV) found themselves with undisputed possession of most of Northern Virginia. The Federal armies had tumbled back into the defenses of Washington in some disarray and the Confederate Capital, Richmond, at least for the time being, was safe. Lee then had to decide what to do next.
Lee could not remain long where he was. Northern Virginia had been largely stripped of food, fodder, and supplies by the Union occupation and hard fighting of the preceding months. He needed to feed and re-supply his troops, but he was also mindful of the very reason his army existed: to achieve the goal of Southern Independence.
One option was to turn South or West, toward Richmond or out to the lush Shenandoah Valley, to rest and provision his army. Though relatively safe, and perhaps logical, this would have been an unlikely choice for Lee. To have done so would have lost the hard-earned military gains of the summer, and returned the initiative to the Federals. Lee was always most effective when he called the shots, and he would not readily give that up.
Another possibility was to attack the Union armies then in Washington. This would also have been a poor choice - Washington was well fortified and manned. As Lee wrote in his letter to President Davis, "I had no intention of attacking him in his fortifications, and am not prepared to invest [surround and siege] them. If I possessed the necessary munitions, I should be unable to supply provisions for the troops". Lee intended to threaten the Capital, but not hit head-on.
The last real choice, then, was to head north into Maryland. Obviously, this is what Lee decided to do, and his plans were approved by President Davis. So what were the factors in Lee's decision? Before now, the Confederate military strategy had strictly been one of defending the borders and territory of the Confederacy, but perhaps this was a good time for a change. There were great risks, to be sure, but also glorious possibilities.
Lee had a number of good reasons for venturing North, and we'll look at them here. First and foremost, as he put it in an 1868 interview, he "went into Maryland to give battle." Whatever else might come from this, he wanted to fight the Federals. He knew there was little chance of winning the war otherwise. Lee's aim was to destroy the enemy, or at least harass him.
Once on Northern soil, the ANV would immediately constitute a threat to Washington and other northern cities, which would force the Army of the Potomac (AOP), George B. McClellan commanding, to come out in pursuit. Lee estimated that the AOP was disorganized and demoralized following the 2nd battle at Bull Run, and that many of the new replacement troops were not yet well trained. This convinced Lee he could get a good jump on the Federals, and meet them somewhere in Maryland on better than even terms in a fight of his choosing.
For the Confederacy, a glittering prize which might be won by a successful campaign was the possibility of military or political intervention by a European power, specifically England or France. There was strong sentiment and political pressure, at least in England, to take some kind of action in the American conflict, presumably taking the part of the Confederate States. There were many in America both north and south who thought that, after the poor Union showing on the Peninsula and at Bull Run, another substantial Rebel victory might be enough to bring the outsiders in. [Note, however, that General Lee did not say this was part of his thinking in making the decision to cross into Maryland - only that it is clear now that European decisions were hanging in the balance that September.]
Lee also hoped that by the presence of his Army he could "liberate" Maryland; help them "throw off the yoke" of Yankee oppression, and bring the state into the Confederacy. A Border state, Maryland had a large and vocal minority who sympathized with the Southern position. If they joined the Confederate States, the Union's Capital would have to be abandoned - surrounded. Even if the state didn't actually secede from the Union, perhaps large numbers of recruits could be added to the army. At the very least, Lee would be able to feed and equip his troops on Northern supplies (to be bought, not taken) rather than those of Virginia.
In addition, Lee calculated that he would be protecting Richmond by keeping the Federals busy in Maryland. He did suggested that if the troops remaining near the Southern Capital were not sufficient, some of General Braxton Bragg's troops (from Tennessee) could be brought East if it seemed the Federals were threatening. Operations in Maryland would also keep the Union forces out of the Shenandoah Valley. The Valley is rich farming country, and was the "breadbasket" of Virginia. The farmers there needed time to bring in the coming harvest, and provide for the next winter. Lee's calculation on this was correct, of course: there wasn't so much as a hint that any Federal force was to be sent south while Lee was in Maryland.
Probably the most important possible benefit, and outcome most desirable to Lee, was the hope that the presence of his army would convince Northern civilians that the war could not be won (or was no longer worth fighting), strengthening the cause of those calling for a negotiated end to the war. Lee had in the back of his mind the possibility that he could present a peace proposal, from a position of strength, that would offer an end to the fighting in exchange for Confederate independence. Although peace discussions of this type did occur later in the war, the Maryland Campaign did not achieve this hope.
When Lee admitted that there was "much risk" in his plan to move north, he meant the real chance that his army would be destroyed in combat or trapped in enemy territory. In fact, his position at Sharpsburg was very nearly a trap: had the battle gone badly and he'd been out-flanked on the northern part of the field, or been cut off from the fords, he would have been hard pressed to get his army safely back to Virginia.
Lee also knew that his Army of Northern Virginia was in sad shape after months of almost continuous campaigning. He noted in his letter to the President that "the army is not properly equipped for an invasion of an enemy's territory. It lacks much of the material of war, is feeble in transportation, the animals being much reduced, and the men are poorly provided with clothes, and in thousands of instances are destitute of shoes..." It would get worse.
When Lee decided to move he had about 60 000 troops on hand. By the time he met McClellan at Sharpsburg, he was down to about 40 000 effectives. Some of the missing were left behind at Winchester VA because, although brave fighters defending Southern ground, they felt it wrong to invade the North. The army also suffered from significant straggling on the roads of Maryland: many soldiers fell out of their units because of sickness, hunger, and exhaustion brought on by a very lean diet of green corn and apples, and strenuous marching, often in bare feet. Many troops were also lost at the South Mountain Gaps on September 14 and in the withdrawal to Sharpsburg following. While Lee may not have anticipated the magnitude of these losses, he knew his army was tired, but still had great confidence that his soldiers were the equal of any number of Federal troops.
It was this confidence, along with all the potential gains, that probably helped General Lee conclude that a drive into Maryland was his best alternative. Even without benefit of the historians' hindsight, it is difficult to see what other choice Lee could have made.
On to Maryland!